Time division multiple access (TDMA) mesh networks require precision timing to achieve energy efficiency by minimizing the time that a radio receiver needs to be turned on to receive a message in its designated time slot from a transmitter. A guard time is added before and after the start of a designated time slot, during which the radio receiver is turned on, to ensure that a transmission is not missed for the case when a receiving node's time keeping is not synchronized with a transmitting node's time keeping. If both clocks are very accurately synchronized, then this guard time can be minimized or even eliminated. Timekeeping clocks for use in mesh networks often use crystal oscillators in which a quartz crystal is resonated using an oscillation circuit such as a Pierce oscillator or a series oscillator. One approach to maintaining synchronization is to have stringent requirements on time keeping crystals so that the timekeeping clocks are accurate and stable especially for different temperatures. For inexpensive low power time keeping crystals, a receiver and transmitter can achieve the stringent requirements using a multi-point calibration over temperature and adjusting the time keeping crystals or timers driven by the crystals for the effects of temperature using the calibration. However, the measurement of a multi-point calibration over temperature is time consuming for these crystals and can lead to high manufacturing costs. Another approach is to purchase temperature stabilized crystals, such as an oven stabilized crystal oscillator, but these crystals can be either more expensive or use more power.